How to resize all pics stored in one folder through ImageMagick

I have different types of pics in one folder. Some of them are GIF, PNG, JPG. I want to resize all the pics stored in that folder to a definite size, say 100*100 in JPG format from command line.

Steps: Browse to the folder where all pics are stored. My all pics are in "Pics" folder located in C drive.
So, I ran the command prompt and browse to
"C:\Pics>"

There ran the command,

C:\Pics>convert *.* -resize 100x100! small.jpg

Now, what this command will do? How it will create different images? Will it overwrite the images as the destination name is same (small.jpg).

This command will pick all the images one by one, whatever be the format and resize them and store them with name small-0.jpg, small-1.jpg, small-2.jpg and such, it will take care of the name itself and will  not overwrite the image. Great ! isn't it.